49cc vs. 80cc

Discussion in 'Spare Parts, Tools & Product Developement' started by John-Forrest, Aug 16, 2009.

  1. John-Forrest

    John-Forrest Member


    This past spring I took out my 49cc engine and put a 80cc on. I am wondering if there is any real difference in power/speed. I did initially note a bit more climbing power, but later that just died down and engine started conking out on very steep inclines.

    I was hoping I'd get 30+ mph, but if I go beyond 20mph, engine rattles like crazy and nuts/bolts start falling out. So I can't really go faster.

    Someone told me that 49 cc works better, he actually put my old 49cc on his bike and said it works great! He suggested I go back to 49cc.

    What are other people's experience with this?


  2. arceeguy

    arceeguy Active Member

    With a 44T rear sprocket (stock with the kit), I have found no real difference in top speed - but the larger 80cc (66cc actual) engines do pull hills better. The 50cc engines seem to run smoother at higher speeds, but this could vary from manufacturer to manufacturer. All these engines look the same on the outside, but some have better internals than others.

    I weigh about 175 lbs, and I can go 32mph on a flat surface and 35 mph down a slight grade. Up a 5% grade, the 50cc slows to about 25 but the 80cc will maintain 28.

    FWIW, I usually putt around town at 20 mph. Great fuel economy, low noise, less surprises from motorists that aren't expecting a bicycle to be doing 30+. I'll open it up on roads with plenty of visibility and light traffic.
  3. motorpsycho

    motorpsycho Active Member

    i have the 49 c.c. slant head 2 stroke engine on a 20" frame with 20" wheels and a 44 tooth sprocket. My friend has the 80 c.c. 2 stroke engine on a 24" frame, with 20" wheels and a 44 tooth sprocket. His motor is broken in, and mine isn't fully broken in yet.
    his gets going from a dead stop better than mine does (more c.c. = more bottom end torque) but i can catch him once we get going and stay side by side with him at 25-28 mph.
    he does weigh more than i do (i am 155 lbs) but even if i ride his 80 c.c. bike, i still get about 25-28 mph top speed out of it.
    i think the 20" wheels takes away from some of the top speed because most bikes with 24" or 26" wheels seem to get a little more top speed than what we're getting with the 20" wheels.
    Last edited: Aug 16, 2009